NO PLIF visualization of transition downstream of a triangular disturbance in a hypersonic flow.

Laser-spectroscopic imaging methods can provide high-quality visualizations of planar slices in hypersonic flows and measure parameters like temperature, velocity, pressure and gas composition without disturbing the flow itself.

The Hypersonics project of the Fundamental Aeronautics Program is developing a method for 2D and 3D imaging of hypersonic flows, called Nitric Oxide Planar Laser-Induced Fluorescence (NO-PLIF). NO-PLIF has been used to study basic transition flow physics relevant to the NASA Hypersonics/ATK HyBoLT experiment and transition control for scramjet engine inlets. It has also been used to study the effects of reaction control system jets, shear layers, wake flowfields, and simulated heat-shield ablation related to high mass Mars entry technology. Additionally, NO PLIF has been used to study the Orion Crew Exploration Vehicle in collaboration with the Constellation program. Moreover, experiments motivated by the Shuttle Return-to-Flight program have included visualizations of flow transition over simulated gap fillers and a detailed study of the breach of the orbiter’s wing leading edge.

Crew Exploration Vehicle (CEV) Wake Flow.

Quantitative measurements using a point-wise technique called Coherent Anti-Stokes Raman Spectroscopy (CARS) have been used to study supersonic combustion flows applicable to scramjet engines. CARS measures temperature and composition and can be used even in ducted engines with limited optical access. CARS has recently been combined with Interferometric Rayleigh Scattering (IRS) to additionally measure two components of velocity. Such measurements are useful for testing and developing new computational models for predicting supersonic combustion. Data obtained in a supersonic combustor using the CARS system has been widely used as a test case for a NATO Research and Technology Organization working group. The current CARS-IRS work is jointly funded by NASA's Fundamental Aeronautics Program and the Office of the Secretary of Defense.

This talk will describe the use and application of three laser-based spectroscopic measurement (NO PLIF, CARS and IRS) techniques to study hypersonic flows and supersonic combustion.

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